Current status of automotive fuel cells for sustainable transport

Automotive proton-exchange membrane fuel cells (PEMFCs) have finally reached a state of technological readiness where several major automotive companies are commercially leasing and selling fuel cell electric vehicles, including Toyota, Honda, and Hyundai. These now claim vehicle speed and acceleration, refueling time, driving range, and durability that rival conventional internal combustion engines and in most cases outperform battery electric vehicles. The residual challenges and areas of improvement which remain for PEMFCs are performance at high current density, durability, and cost. These are expected to be resolved over the coming decade while hydrogen infrastructure needs to become widely available. Here, we briefly discuss the status of automotive PEMFCs, misconceptions about the barriers that platinum usage creates, and the remaining hurdles for the technology to become broadly accepted and implemented.     

Photo-responsive metal/semiconductor hybrid nanostructure:A promising electrocatalyst for solar light enhanced fuel cell reaction

Direct alcohol fuel cells(DAFCs) have received wide attention as a new type of clean energy device because of their high energy conversion efficiency,portability,non-toxicity and pollution-free.Anode catalysts are the key factors affecting the performance of DAFCs.Recently studies show that using the optical activity of semiconductor materials as the carriers of traditional precious metal electrocatalysts,under the illumination of light sources,can greatly improve the electrocatalytic activity and stability of electrodes.In this review,the research progress of photo-responsive metal/semiconductor hybrids as the electrocatalysts for DAFCs in recent years is summarized,including:(1) Mechanism and advantages of photo-assistant electrochemical alcohol oxidation reaction,(2) me tal/semiconductor electrocatalyst for the different type of fuel cell reactions,(3) different kind of metals in photo-responsive metal/semiconductor hybrid nanostructure,(4) the personal prospects of the photo-responsive metal/semiconductor electrode for future application in DAFCs.     

高活性、低载量的PtCo/C质子交换膜燃料电池催化剂的合成

利用逐步合成的方法,合成了一系列不同量硝酸处理的PtCo/C催化剂.通过燃料电池测试装置对催化剂进行了测试,结果表明PtCo/C催化剂在较低载量情况下,有着很好的性能:在50 kPa背压下,0.9 V下的电流密度达到44 mA·cm-2,0.8 V下的电流密度超过300 mA·cm-2;200 kPa背压下,最高功率密...     

氨能源作为清洁能源的应用前景

合成氨是一种成本低廉的化工原料,具有较高能量密度和辛烷值、易于压缩储运、燃烧不产生CO2等优点,是一种应用前景广泛的新型清洁能源。氨既可替代汽油、柴油等化石燃料,为汽车发动机直接提供清洁燃料,也可以经催化分解制取氢气,为车载燃料电池提供安全氢气。作为传统石油燃料的理想替代品,氨为解决环境污染和能源短缺问题提供了新的燃料选择。本文主要从发动机燃料和燃料电池原料两方面,介绍氨用于汽车动力源的优越性和可操作性,以及国内外相关研究进展;集中分析了氨分解制氢的催化剂体系的研究进展和局限性,以及合成氨的研究现状。     

Water management improvement in PEM fuel cells via addition of PDMS or APTES polymers to the catalyst layer

Water management is one of the obstacles in the development and commercialization of proton exchange membrane fuel cells (PEMFCs). Sufficient humidification of the membrane directly affects the PEM fuel cell performance. Therefore, 2 different hydrophobic polymers, polydimethylsiloxane (PDMS) and (3-Aminopropyl) triethoxysilane (APTES), were tested at different percentages (5, 10, and 20 wt.%) in the catalyst layer. The solution was loaded onto the surface of a 25 BC gas diffusion layer (GDL) via the spraying method. The performance of the obtained fuel cells was compared with the performance of the commercial catalyst. Characterizations of each surface, including different amounts of PDMS and APTES, were performed via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses. Molecular bond characterization was examined via Fourier transform infrared spectroscopy (FTIR) analysis and surface hydrophobicity was measured via contact angle measurements. The performance of the fuel cells was evaluated at the PEM fuel cell test station and the 2 hydrophobic polymers were compared. Surfaces containing APTES were found to be more hydrophobic. Fuel cells with PDMS performed better when compared to those with APTES. Fuel cells with 5wt.% APTES with a current density of 321.31 mA/cm ² and power density of 0.191 W/cm ² , and 10wt.% PDMS with a current density of 344.52 mA/cm ² and power density of 0.205 W/cm ² were the best performing fuel cells at 0.6V.     

Investigation of the stability of Co-doped apatite ionic conductors in NH3

Hydrogen powered solid oxide fuel cells (SOFCs) are of enormous interest as devices for the efficient and clean production of electrical energy. However, a number of problems linked to hydrogen production, storage and transportation are slowing down the larger scale use of SOFCs. Identifying alternative fuel sources to act as intermediate during the transition to the full use of hydrogen is, therefore, of importance. One excellent alternative is ammonia, which is produced on a large scale, is relatively cheap and has the infrastructure for storage and transportation already in place. However, considering that SOFCs operate at temperatures higher than 500 °C, a potential problem is the interaction of gaseous ammonia with the materials in the cathode, anode and solid electrolyte. In this paper, we extend earlier work on high temperature reactions of apatite electrolytes with NH₃ to the transition metal (Co) doped systems, La_9.67Si₅CoO₂₆ and La₁₀(Si/Ge)₅CoO_26.5. A combination of PXRD, TGA and XAFS spectroscopy data showed a better structural stability for the silicate systems. Apatite silicates and germanates not containing transition metals tend to substitute nitride anions for their interstitial oxide anions, when reacted with NH₃ at high temperature and, consequentially, lower the interstitial oxide content. In La_9.67Si₅CoO₂₆ and La₁₀(Si/Ge)₅CoO_26.5 reduction of Co occurs as a competing process, favouring lower levels of nitride-oxide substitution.     

Platinum group metal-free Fe-based (FeNC) oxygen reduction electrocatalysts for direct alcohol fuel cells

In direct alcohol fuel cells (DAFCs), the oxidation of alcohols happens at the expenses of the oxygen reduction reaction at the cathode. DAFCs' cathodes use a significant amount of platinum that is an expensive critical raw material. Moreover, platinum oxidizes alcohols, a fact that combined with alcohol crossover, decreases significantly the performance of the cells. The use of Fe-based (FeNC) platinum group metal–free (PGM-free) cathodes is a convenient strategy to overcome these limitations. This review analyzes the application of PGM-free cathodes to DAFCs. The discussion focuses on acidic systems and covers the following subjects: (i) the breakdown of DAFC potential in its components, (ii) the analysis of the advantages from the use of the PGM-free cathode, and (iii) a review of the performance and durability of DAFCs. The review closes with a view of the authors of the future perspective for the research.     

Performance Assessment of a Perfluorosulfonic Acid‐type Membrane (i. e. Nafion™ 115) for an Enzymatic Fuel Cell

A high power enzymatic fuel‐cell was anticipated by using a recently developed glucose oxidase (GOx) immobilized bio‐anode, a conventional platinum?carbon based cathode and a popular high performance 125 μ‐thick perfluorosulfonic acid‐type proton exchange membrane (i. e. Nafion® 115). Unexpected current density decay from 2.13 mA cm^?2 to 0.28 mA cm^?2 was observed within 2 hours. Polarization measurements and AC impedance analysis indicated that loss of performance was linked to the membrane behavior. Ion exchange between buffer solution and membrane was perceived as the main cause for the fast performance loss. Saturation of the membrane with the cation in the buffer solution diminished proton transfer needed for cathode reaction. Charge transfer resistances, obtained from AC impedance data, increased with time substantially due to cation exchange within membrane. Replacement of membrane with the same enzyme electrode and cathode has resulted 100 % current density recovery on the fuel cell performance. It was concluded that a membrane, not affected by the buffer cations, was required for successful enzymatic fuel cell applications.     

Highly Dispersed and Nano-sized Pt-based Electrocatalysts for Low-Temperature Fuel Cells

Among metals, Pt is so far the best material to be used as anode and cathode in low-temperature fuel cells. However, Pt has the drawback of being expensive and easily CO-poisoned. Thus, to produce useful electrocatalysts, significant efforts have been made worldwide on developing Pt-based catalysts with low Pt contents as well as searching for alternative materials with high catalytic activity for anodic and cathodic reactions in low-temperature fuel cells. This article presents the development of highly dispersed and nano-sized Pt-based electrocatalysts synthesized by several new methods based on our experimental results. In the case of anode materials, our proposed new method consists of the synthesis of Pt-based nanoparticles in order to maximize their surface availability, combined with the use of secondary metals that promote the oxidations of methanol and CO. On the other hand, for the cathode materials, the use of the Pt catalysts mixed with metal oxides enhances their oxygen reduction reaction (ORR) activity. We anticipate that the highly dispersed Pt-based nanoparticles introduced in this article will improve the performance of anode and cathode for low-temperature fuel cells.     

Effect of load-cycling amplitude on performance degradation for proton exchange membrane fuel cell

Durability is one of the critical issues to restrict the commercialization of proton exchange membrane fuel cells (PEMFCs) for the vehicle application. The practical dynamic operation significantly affects the PEMFCs durability by corroding its key components. In this work, the degradation behavior of a single PEMFC has been investigated under a simulated automotive load-cycling operation, with the aim of revealing the effect of load amplitude (0.8 and 0.2 A/cm² amplitude for the current density range of 0.1−0.9 and 0.1−0.3 A/cm², respectively) on its performance degradation. A more severe degradation on the fuel cell performance is observed under a higher load amplitude of 0.8 A/cm² cycling operation, with ∼10.5% decrease of cell voltage at a current density of 1.0 A/cm². The larger loss of fuel cell performance under the higher load amplitude test is mainly due to the frequent fluctuation of a wider potential cycling. Physicochemical characterizations analyses indicate that the Pt nanoparticles in cathodic catalyst layer grow faster with a higher increase extent of particle size under this circumstance because of their repeated oxidation/reduction and subsequent dissolution/agglomeration process, resulting in the degradation of platinum catalyst and thus the cell performance. Additionally, the detected microstructure change of the cathodic catalyst layer also contributes to the performance failure that causes a distinct increase in mass transfer resistance.     

Scandia-stabilized zirconia-impregnated (La,Sr)MnO3 cathode for tubular solid oxide fuel cells

We have studied the properties of a LSM-ScSZ composite cathode fabricated by a two-step process including dip-coating LSM framework and ion-impregnating ScSZ, for using with anode-supported tubular solid oxide fuel cells. A preliminary examination of the single tubular cell, consisting of a Ni-YSZ anode support tube, a Ni-ScSZ anode functional layer, a ScSZ electrolyte film, and a LSM-ScSZ cathode fabricated by ion-impregnating, has been carried out, and an improved performance was obtained. The polarization resistance of the cathode side clearly decreased for impregnating the electronic conducting phase (LSM) with the ionic conducting phase (ScSZ). And the single cell with the impregnated cathode generated a maximum power density of 433 mW cm⁻² at 850 °C, when operating with humidified hydrogen.     

高分散Fe-N-C氧还原反应电催化剂及其在直接甲醇燃料电池中的应用

氧还原反应(ORR)是燃料电池和金属空气电池等洁净发电装置中阴极的主要反应,该反应动力学过程慢,电化学极化严重. Pt基电催化剂具有较好的ORR活性,然而Pt资源有限、价格昂贵,研制高活性、低成本的代Pt电催化剂意义重大.经过几十年的探索,研究者发现将含有C, N和Fe等元素的前体进行高温热处理得到的Fe-N-C电催化剂对ORR具有良好的活性,然而在高温热解过程中Fe容易发生聚集而形成大块颗粒,导致Fe的利用率不高,影响了电催化剂的ORR活性.
　　本文分别以聚吡咯和乙二胺四乙酸二钠(EDTA-2Na)为C和N的前驱体,利用高温热解形成的富含微孔的碳材料对铁前体的吸附及锚定作用,获得了一种Fe高度分散的Fe-N-C电催化剂.采用物理吸脱附技术、高分辨透射电镜(HRTEM)和扫描电镜对Fe-N-C及其制备过程中相关电催化剂的孔结构及表面形貌进行了表征.结果表明,在第一步热解过程中, EDTA-2Na的Na对碳材料起到了活化作用,形成富含微孔的N掺杂碳材料(N-C-1),其BET比表面积达到1227 m2/g,孔径约1.1 nm.在第二步热解过程中, N-C-1有效地抑制了Fe的聚集,产物Fe-N-C中的Fe元素均匀地分布在碳材料中,其比表面积高达1501 m2/g.
　　电化学测试结果表明,在碱性介质(0.1 mol/L NaOH)中, Fe-N-C电催化剂对ORR具有良好的催化活性, ORR起始电位(Eo)为1.08 V (vs. RHE),半波电位(E1/2)0.88 V,电子转移数n接近4, H2O2产率<3%,与商品20%Pt/C(Johnson Matthey)接近.电化学加速老化测试结果表明, Fe-N-C的E1/2未发生明显变化,而Pt的负移45 mV,表明Fe-N-C具有很好的稳定性;在酸性介质(0.1 mol/L HClO4)中, Fe-N-C的Eo为0.85 V, E1/2为0.75 V,其E1/2比Pt/C负移约0.15 V,表明在酸性介质中Fe-N-C对ORR的催化活性还有待提高.采用TEM、X射线衍射、X射线光电子能谱以及穆斯堡尔谱等方法研究了电催化剂构效关系.结果表明, Fe-N-C较好的ORR活性主要来自于高分散的Fe-N4结构,此外, N(吡啶N和石墨N)掺杂的C也对反应具有一定的催化活性.
　　与Pt/C相比, Fe-N-C电催化剂具有很好的耐甲醇性能.本文对比了Fe-N-C和Pt/C作为阴极催化剂的直接醇类燃料电池(DMFC)性能,采用质子交换膜的DMFC最大功率密度分别为47(Fe-N-C)和79 mW/cm2(Pt/C),而采用碱性电解质膜的则分别为33(Fe-N-C)和8 mW/cm2(Pt/C).结合半电池结果表明, Fe-N-C电催化剂在碱性介质中具有比Pt更为优秀的催化活性和稳定性,有望用作DMFC阴极代Pt催化剂.     

Determination of trace organic chlorides in hydrogen for fuel cell vehicles by gas chromatography coupled with ion mobility spectrometry

A method for the determination of organic chlorides in hydrogen for fuel cell vehicles by gas chromatography coupled with ion mobility spectrometry was established. Organic chlorides were separated by a non-polar gas chromatography column and detected in the negative ion mode of the ion mobility spectrometer. The effect of operating parameters of ion mobility spectrometer including drift gas flow rate and drift tube temperature on sensitivity and resolution were evaluated. Under the optimized conditions, the detection limits of seven organic chlorides were from 0.65 to 6.73 nmol/mol, which met the requirement of detection for the specification limit of 50 nmol/mol of total halogen impurities in hydrogen for fuel cell vehicles. Compared with gas chromatography-mass spectrometry, and gas chromatography coupled with electron capture detector under the same gas chromatography conditions, gas chromatography coupled with ion mobility spectrometry method demonstrated higher sensitivity for detection of organic chlorides under study. Based on the portability of the device and its detection capabilities, gas chromatography coupled with ion mobility spectrometry has the potential to perform online detection of impurities in hydrogen for fuel cell vehicles.     

Rare earth hydrogen storage alloy used in borohydride fuel cells

Fuel cell using the borohydride as the fuel has attracted much attentions because of high energy density and working potential. In this work, LaNi_4.5Al_0.5 hydrogen storage alloy used as the anodic material to replace noble metals has been investigated. Experimental results showed that H₂ evolution was unavoidable during discharge process because of the hydrolysis of , but the utilization of the fuel increased with the increasing current densities. At high discharge current, the alloy electrode showed the lowest hydrogen generation rate and higher utilization of the fuel because, the generated hydrogen was absorbed and oxidized to produce electric energy similar to the behavior of hydrogen storage alloy in nickel–metal hydride batteries. The reaction mechanism of borohydride on the surface of electrode made of hydrogen storage alloy also has been discussed. Hydrogen storage alloy would be a promising material as the anodic catalyst in borohydride fuel cell.     

A Hydrazine-Nitrate Flow Battery Catalyzed by a Bimetallic RuCo Precatalyst for Wastewater Purification along with Simultaneous Generation of Ammonia and Electricity

The traditional technologies for industrial and agricultural effluent treatment are often energy-intensive. Herein, we suggest an electrochemical redox strategy for spontaneous and simultaneous decontamination of wastewater and generation of both fuels and electricity at low cost. Using hydrazine and nitrate effluents as a demonstration, we propose a hydrazine-nitrate flow battery (HNFB) that can efficiently purify the wastewater and meanwhile generate both ammonia fuel and electricity with the assistance of our developed bimetallic RuCo precatalyst. Specifically, the battery delivers a peak power density of 12 mW cm⁻² and continuously operates for 20 h with an ammonia yield rate of ca. 0.38 mmol h⁻¹ cm⁻² under 100 mA cm⁻². The generated electricity can further drive a hydrazine electrolyzer to produce hydrogen fuel. Our work provides an alternative pathway to purify wastewater and generate high value-added fuels at low cost.     

采用甲烷燃料的管状固体氧化物燃料电池浸渍阳极电化学性能

以NiO和8％（摩尔分数）氧化钇稳定的氧化锆为原料,采用注凝成型工艺制备了管状同体氧化物燃料电池阳极支撑体．用离子浸渍法对阳极支撑体进行表面修饰．用电化学工作站测单电池交流阻抗和输出性能并且用化学气相色谱仪对电池尾气进行分析．测试结果表明修饰后的阳极在通甲烷的情况下出现了一定程度的积炭,但是积炭现象在一定的测试时间内达到平衡,没有对电池造成破坏,并且显著地提高了电池阳极的电化学性能．单电池存通入氯气和甲烷的情况下最大输出功率密度分别达到了225和400mW／cm^2．     

Improvement in performance of a direct ethanol fuel cell: Effect of sulfuric acid and Ni-mesh

A direct ethanol fuel cell (DEFC) is developed with low catalyst loading at anode and cathode compared to that reported in the literature. Pt/Ru (40%:20% by wt.)/C and Pt-black were used as anode and cathode catalyst with loadings in the range of 0.5–1.2 mg/cm². The temperatures of anode and cathode were varied from 34 °C to 110 °C, and the pressure was maintained at 1 bar. Although low catalyst loading was used, the cell performance is enhanced by 40–50% with the use of low concentration of sulfuric acid in ethanol and Ni-mesh as current collector at the anode. The power density 15 mW/cm² at 32 mA/cm² of current density is obtained from the single cell with 0.5 mg/cm² loading of Pt–Ru/C at anode (90 °C) and Pt-black at cathode (110 °C). The performance of DEFC increases with the increase in ethanol and sulfuric acid concentrations, electrocatalyst loadings up to 1 mg cm⁻² at anode and cathode. However, the performance of DEFC decreases with further increase in electrocatalyst loading.     

Effect of Anode Material on Electrochemical Oxidation of Low Molecular Weight Alcohols—A Review

The growing climate crisis inspires one of the greatest challenges of the 21st century—developing novel power sources. One of the concepts that offer clean, non-fossil electricity production is fuel cells, especially when the role of fuel is played by simple organic molecules, such as low molecular weight alcohols. The greatest drawback of this technology is the lack of electrocatalytic materials that would enhance reaction kinetics and good stability under process conditions. Currently, electrodes for direct alcohol fuel cells (DAFCs) are mainly based on platinum, which not only provides a poor reaction rate but also readily deactivates because of poisoning by reaction products. Because of these disadvantages, many researchers have focused on developing novel electrode materials with electrocatalytic properties towards the oxidation of simple alcohols, such as methanol, ethanol, ethylene glycol or propanol. This paper presents the development of electrode materials and addresses future challenges that still need to be overcome before direct alcohol fuel cells can be commercialized.     

管式电解质支撑型直接碳固体氧化物燃料电池的浸渍法制备及电性能

管状电解质支撑型固体氧化物燃料电池(SOFC)具有稳定性高、电极选择范围广、易封接等优点,很适合应用于直接碳固体氧化物燃料电池(DC-SOFC)现阶段的基础研究中。为实现管状电解质支撑型SOFC的便捷制备,本研究开发了管状YSZ(钇稳定化氧化锆)电解质支撑膜的浸渍法制备工艺。组装了电极材料为Ag-GDC(钆掺杂氧化铈)的电解质支撑型SOFC单电池。测试了单电池分别以加湿氢气和担载5%(w,质量分数)Fe的活性炭为燃料,环境空气为氧化剂的电性能。电池的开路电压接近理论值,且扫描电镜分析结果表明电解质膜致密。单电池以活性碳为燃料在800°C取得了280 m W?cm~(-2)的最大功率密度,接近其以加湿氢气为燃料的330 m W?cm~(-2)。交流阻抗谱结果表明YSZ电解质的欧姆电阻是影响电池性能的主要原因。DC-SOFC以恒电流1 A放电,运行了2.1 h,燃料利用率为36%。DC-SOFC二次装载碳燃料后的电性能几乎与初次的性能一样,表明制备的YSZ电解质支撑膜可稳定的应用于DC-SOFCs中。分析了DC-SOFC放电过程中电性能衰减的机制。     

Effect of cosintering of anode–electrolyte bilayer on the fabrication of anode-supported solid oxide fuel cells

A comparative study is carried out on the effect of cosintering temperature of anode–electrolyte bilayer on the fabrication and cell performance of anode-supported solid oxide fuel cells from commercially available tape casting materials. It was found that the sintering conditions have profound effects on the anode characteristic and cell performance. For low cosintering temperature as low as 1,250 °C, the electrolyte is unable to sinter fully and forms a porous structure which leads to a reduced open-circuit potential and poor cell performance especially under low current output. For further increasing cosintering temperature to 1,350 °C, the cell performance was lower under low current operation. However, the cell performance turns out to be better than that of high-temperature cosintering under high current output. Although at temperature as high as 1,500 °C the cell performs better than that of low temperature cosintering, the trend turn out to be reverse for high current operating due to less anode surface area resulting from overagglomeration of anode layer. An optimal cosintering temperature of 1,350–1,450 °C is recommended for commercially available anode–electrolyte bilayer of anode-supported solid oxide fuel cells.